[code-quality] Proposal to extend pylintrc syntax to allow multiple disable/enable parameters

[Michael Overmeyer]

Hello,

I'm trying to set up my build system to use pylintrc files during the build. 
For example, in my pylintrc file I was going to do something like:

```
disable=all 
enable=E 
disable=import-error
```

Which (of course) doesn't work:

```
$>pylint --rcfile=pylintrc my_file.py
    <stacktrace truncated>
    backports.configparser.DuplicateOptionError: While reading from 'pylintrc' [line 24]: option u'disable' in section u'MESSAGES CONTROL' already exists
```

Once I realised that they are INI files, it made more sense. INI files do not allow for multiple values for a key (within a section), and different parsers handle this case differently.
Since strict=True was being used by the Python parser, it raise this exception.

The annoying part is that you can pass multiple 'enable/disable' arguments on the command line.
In fact, there is an example in the documentation auto-generated by `pylint --generate-rcfile`: 

    "If you want to run only the classes checker, but have no Warning level messages displayed, use '--disable=all --enable=classes --disable=W'"
    
But this cannot be done in the pylintrc file. Annoying, since I was not going to use the command line and changing my build system to do would be non-trivial.

I would like to see the pylintrc file have at least as much capability as the command line. I would like to propose to extend the syntax to provide an ordering.

Proposal:

Today we have "disable" and "enable", with "enable" taking precedent.
Perhaps we could change the syntax to be "disableX" "enableY", with X and Y being positive integers. Higher precedence would be determined by higher integers. "enable" would still have precedent within a given integer level.

It would be backwards compatible, with 'disable' being an alias for 'disable1' and 'enable' being an alias for 'enable1'.

Some examples:

```
disable=all
enable=classes
disable2=W
```

would be equivalent to:

```
disable1=all
enable1=classes
disable2=W
```

There could easily be a better way to do that this, or some pattern/syntax people already use when dealing with INI files in order to work around this.
I would like to see the pylintrc file have at least as much capability as the command line.

Let me know what you think,

Michael Overmeyer

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